1. Field of the invention
The present invention relates to a drive device for optical system equipped in an image forming equipment such as, for example, a document copying machine, etc.
2. Description of the Prior Art
Generally, in this kind of image forming equipment, an optical system is arranged below the lower side of a document table, and the optical system is reciprocatably supported by rails laid in parallelism with the document table within a specified area between an original position (home position) and a return position on the rails. The optical system is driven by, for example, a servo motor, and the servo motor is controlled for drive and stop with availability and unavailability of power supply to the servo motor.
A magnification lens is provided on an optical path from the optical system to a photosensitive body, and electrostatic latent image can be formed at a specified ratio of magnification on the surface of the photosensitive body by adjusting the movement of the lens along the optical path and at the same time carrying out scanning with the optical system.
Hereupon, in that case, although the optical system is driven to move as making the above original position as reference, existence of the optical system at the original position is detected by a so-called home position switch which is provided thereat.
And when the home position switch is in the OFF status in the event that the power source of the corresponding equipment is turned ON, the optical system is once driven and shifted to the paper feed side and subsequently is driven to move in the paper delivery side since it is not clear at which position the optical system exists, i.e., the paper feed side or the paper delivery side. This is called a so-called initial action. The above home position switch is turned ON with this action, and the processing for making the optical system move to the original position for correction is carried out. Therefore, when the home position switch is already turned ON in the case that the power source is turned ON, the above initial action is not performed.
Hereupon, in such image forming equipment, in the event that during image forming action, for example, paper jamming occurs or a cover attached to the box-like body is opened, power supply to internal devices of the corresponding equipment is immediately shut off, for the purpose of preventing the equipment from being damaged or taking danger to an operator into consideration.
Therefore, in the case that the optical system is positioned in the vicinity of the turning-back point within the above specified area during stoppage of the power supply, the optical system is likely to move by inertia since the power supply to the servo motor is stopped, and there is a possibility for the optical system to come into collision with the box-like body, lens, etc. Although it is better that the size of the box-like body is determined, taking the travelling distance of the optical system by inertia into consideration, it will never be a solution best-suited to the reality under such circumstances that compactness of machines and moreover high processing speed of image forming are recently in progress.
Furthermore, if the above initial action is carried out when the power supply is started again after for example, treatment for the above paper jamming is finished, there will be a possibility for the optical system to come into collision with the box-like body, the lens, etc.